This contract is for the performance of cell culture cytotoxicity tests using the Eagle-Foley tube assay with the KB cell line. Objectives: presumptive screening plant materials for follow-up testing of active natural products as a tool for fractionation; presumptive screening of synthetic materials when quantity available is insufficient to conduct in vivo testing. Presumptive screening is done for all new plant materials. Those plant product samples having confirmed in vivo activity are tested to ascertain existence of correlation with this in vivo activity. Fractionation of materials having both in vivo and in vitro activity is followed with the KB assay.